High-frequency power amplifier

ABSTRACT

A high-frequency power amplifier that amplifies a high-frequency input signal and outputs a signal having one power selected from a plurality of powers includes a high output route that is a circuit, which amplifies the input signal and outputs a signal of a high power, and a medium output route that is a circuit, which amplifies the input signal and outputs a signal of a medium power. The high output route includes a high-output amplifier that amplifies the input signal, an output matching circuit that is connected to an output node of the high-output amplifier, and a switch element that is connected to an output node of the output matching circuit. The medium output route includes a medium-output amplifier that amplifies the input signal and a switch element that is connected between an output node of the medium-output amplifier and an output node of the output matching circuit.

BACKGROUND

1. Technical Field

The present invention relates to a high-frequency power amplifier and,particularly to a wide-band high-frequency power amplifier that issuitable for transmission of a mobile communication device including amobile phone.

2. Background Art

In recent years, for mobile communication devices such as mobile phones,there is a strong demand for multiband in which a plurality of frequencybands are used because of reservation of a communication capacity andglobal roaming. Currently mainstream communication systems include asecond generation system in which GSM (Global System for MobileCommunications) is adopted and a third generation system in which CDMA(Code Division Multiple Access) is adopted. Band I ranging from 1920 MHzto 1980 MHz, Band II ranging from 1850 MHz to 1910 MHz, Band III rangingfrom 1710 MHz to 1785 MHz, Band IV ranging from 1710 MHz to 1755 MHz,Band V ranging from 824 MHz to 849 MHz, Band VI ranging from 830 MHz to840 MHz, Band VIII ranging from 880 MHz to 915 MHz, Band IX ranging from1749.9 MHz to 1784.9 MHz, and Band XI ranging from 1427.9 MHz to 1452.9MHz exist as the frequency band used in transmission of thecommunication systems. A combination of the communication system and acommunication frequency differs in various regions where the mobilephone is used.

In such multiband mobile phones, in addition to downsizing of a battery,it is necessary that efficiency (power saving) of transmission poweramplifier in which a power consumption ratio is high be improved inorder to achieve downsizing, weight reduction, and prolonged talk. AGaAs high-frequency transistor excellent in a high-frequencycharacteristic and power conversion efficiency is mainly used as thetransmission power amplifier for the mobile phone. The GaAshigh-frequency transistor is roughly classified into a field effecttransistor (hereinafter referred to as an FET) and a heterojunctionbipolar transistor (hereinafter referred to as an HBT).

In CDMA systems such as W-CDMA, a technique of controlling thehigh-frequency power output from an antenna of the mobile terminalaccording to a distance to a base station or an ambient environment isused such that the high-frequency power reaching the base station issubstantially equalized. Generally, the antenna output increases in thecase that the mobile terminal is far from the base station, and theantenna output decreases in the case that the mobile terminal is closeto the base station. The antenna output is performed by controlling theoutput of a PA (Power Amplifier) module (hereinafter referred to as a“high-frequency power amplifier”). Frequently the mobile terminal isused while the antenna output is suppressed to a relatively low level,and it is necessary to achieve the high efficiency of the high-frequencypower amplifier in a low output condition in order to reduce the powerconsumption. However, the high-frequency power amplifier is designedsuch that power efficiency is maximized during high output. Therefore,the power efficiency is degraded in the output power below the highoutput.

A high-frequency power amplifier that switches an output route usedaccording to the required output power is proposed as a technology ofimproving the efficiency during medium output and low output (see U.S.Patent Publication No. 2007/0222523). FIG. 9 is a block diagram ofhigh-frequency power amplifier 29 disclosed in U.S. Patent PublicationNo. 2007/0222523.

Conventional high-frequency power amplifier 29 will be described belowwith reference to FIG. 9. Note that, in the following description, thesame element is designated by the same numeral. High-frequency poweramplifier 29 includes input terminal 1, output terminal 2, bias/controlcircuit 3, high output route 10, medium output route 100, low outputroute 110, and output matching circuit 13.

An operation of high output route 10 will now be described. Ahigh-frequency power signal input from input terminal 1 is input tohigh-output amplifier 11 through input matching circuit 12, andamplified. The high-frequency power signal amplified by high-outputamplifier 11 is output from output terminal 2 through output matchingcircuit 13.

Next, the operation of medium output route 100 will be described. Thehigh-frequency power signal input from input terminal 1 is input tomedium-output amplifier 111 through input matching circuit 112. Thehigh-frequency power signal amplified by medium-output amplifier 111 isoutput from output terminal 2 through output matching circuit 113,switch element 114, and output matching circuit 13.

Next, the operation of low output route 110 will be described. Thehigh-frequency power signal input from input terminal 1 is input tolow-output amplifier 211 through input matching circuit 212. Thehigh-frequency power signal amplified by the low-output amplifier 211 isoutput from output terminal 2 through output matching circuit 213,switch element 214, output matching circuit 113, switch element 114, andoutput matching circuit 13 in turn. Which one of three output routes 10,100, and 110 amplifies the high-frequency power signal input from inputterminal 1 is determined by bias/control circuit 3, which performscontrol of a bias current to amplifiers 11, 111, and 211 and control ofswitch elements 114 and 214.

Thus, the conventional high-frequency power amplifier 29 switches theoutput route used according to the required output power.

SUMMARY

However, in the circuit configuration of the conventional high-frequencypower amplifier 29, unfortunately it is necessary to provide outputmatching circuit 113 in medium output route 100 and output matchingcircuit 213 in low output route 110. That is, it is necessary to provideoutput matching circuit 113 and 213 in medium and low output routes 100and 110 in order to optimize an output impedance in other output routes(medium and low output routes 100 and 110) according to the extremelylow output impedance of high output route 10. At least two componentsare required in each of output matching circuits 113 and 213. Generallythe high-frequency matching circuit is configured by an inductor or acapacitor. However, the frequency band of the high-frequency matchingcircuit is restricted because the inductor or the capacitor has afrequency characteristic. It is necessary to optimize a value of theinductor or capacitor according to the frequency. Therefore, in themultiband, it is necessary to provide a medium-output route or alow-output route in each band (that is, the matching circuit in eachband). In the case that the matching circuit is configured by at leastthree components in order to widen the band, a circuit scale is furtherenlarged, and a loss also increases, which results in a problem in thatthe power efficiency is degraded.

The present invention has been devised in order to solve the aboveproblem and an object thereof is to provide a high-frequency poweramplifier that can output the signal having the power selected from theplurality of powers without enlarging the circuit scale.

In accordance with an aspect of the present invention, a high-frequencypower amplifier amplifies a high-frequency input signal and outputs asignal having one power selected from a plurality of powers, thehigh-frequency power amplifier includes: a first output route that is acircuit, which amplifies the input signal and outputs a signal of afirst power; and a second output route that is a circuit, whichamplifies the input signal and outputs a signal of a second power,wherein the first output route includes: a first amplifier thatamplifies the input signal; a first output matching circuit that isconnected to an output node of the first amplifier; and a first switchelement that is connected to an output node of the first output matchingcircuit, and the second output route includes: a second amplifier thatamplifies the input signal; and a second switch element that isconnected between an output node of the second amplifier and an outputnode of the first output matching circuit. Because the output node ofthe first output matching circuit in the first output route and theoutput node of the second amplifier in the second output route areconnected to each other (through the switch element), a difference inoutput impedance corresponding to a difference in output power betweenthe first amplifier and the second amplifier can be absorbed by the oneoutput matching circuit (the first output matching circuit). Therefore,in the second output route, the necessity of the output matching circuitthat converts the output impedance of the second amplifier is eliminatedto reduce the circuit scale. Additionally, in the second output route,it is not necessary to provide the output matching circuit configured bythe inductor and capacitor having the frequency characteristic.Therefore, the wide-band amplifier circuit is configured.

In an example of a relationship between the first power and the secondpower, preferably the first power is larger than the second power, eachof the first amplifier and the second amplifier is configured by atransistor, and a cell size of the transistor constituting the firstamplifier is larger than a cell size of the transistor constituting thesecond amplifier. At this point, an input impedance of the first outputmatching circuit may be lower than an input impedance of the secondswitch element, or each of the first switch element and the secondswitch element may configured by a transistor and a size of the firstswitch element may be larger than a size of the second switch element.The output impedance of the first output matching circuit is equalizedto the output impedance of the second amplifier, and the outputimpedance of the first output matching circuit is matched with theoutput impedance of the second amplifier. Therefore, it is not necessaryto provide the output matching circuit in the output node of the secondamplifier.

Preferably the second switch element is configured by transistors thatare connected in a plurality of stages. Specifically, preferably thesecond switch element is configured by connecting in series a pluralityof circuits, each of which is configured by a transistor and a resistorbeing connected in parallel. Therefore, isolating can highly bemaintained between the output terminal of the first output route and thesecond amplifier of the second output route, and the output efficiencyis highly maintained during the output of the first power.

The high-frequency power amplifier may further include an input terminalto which the input signal is input, wherein the second output route mayfurther include a third switch element that is connected between theinput terminal and an input node of the second amplifier. At this point,preferably the first output route further includes a fourth switchelement that is connected between the input terminal and an input nodeof the first amplifier. Therefore, the isolation can highly bemaintained in the input node of the first output route and the inputnode of the second output route, and the input signal is surely input tothe desired output route without losing the power.

The high-frequency power amplifier may further include an outputterminal that is connected between the output node of the first switchelement and the output node of the second switch element. At this point,preferably the high-frequency power amplifier further includes: anoutput terminal that outputs an output signal from the high-frequencypower amplifier; and a capacitor that is connected between the outputterminal and a connection point of the output node of the first switchelement and the second switch element. Therefore, in the signal outputfrom the first amplifier or second amplifier, only an AC component isoutput from the output terminal.

The high-frequency power amplifier may include the plurality of firstoutput routes corresponding to different frequency bands. Therefore, thehigh-frequency power amplifier that is ready for the multiband and thetwo power outputs can be configured.

In the present invention, the circuit scale can be reduced in thehigh-frequency power amplifier that operates by selecting one of theplurality of output routes according to the required output power.Therefore, a practical value of the present invention is significantlyhigh because the multiband mobile phone in which the plurality of outputroutes need to be switched in the high-frequency power amplifier isbecoming increasingly common.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of a high-frequency power amplifier accordingto a first embodiment of the present invention.

FIG. 2 is a circuit diagram of the high-frequency power amplifieraccording to the first embodiment of the present invention.

FIG. 3 is a block diagram of a high-frequency power amplifier accordingto a second embodiment of the present invention.

FIG. 4 is a circuit diagram of the high-frequency power amplifieraccording to the second embodiment of the present invention.

FIG. 5 is a block diagram of a high-frequency power amplifier accordingto a third embodiment of the present invention.

FIG. 6 is a block diagram of a high-frequency power amplifier accordingto a fourth embodiment of the present invention.

FIG. 7 is a block diagram of a high-frequency power amplifier accordingto a fifth embodiment of the present invention.

FIG. 8 is a block diagram of a high-frequency power amplifier accordingto a sixth embodiment of the present invention.

FIG. 9 is a block diagram of a high-frequency power amplifier of aconventional technology.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a high-frequency power amplifier according to an embodimentof the present invention will be described with reference to thedrawings.

First Exemplary Embodiment

FIG. 1 is a block diagram of high-frequency power amplifier 21 accordingto a first embodiment of the present invention. FIG. 2 is a viewillustrating an example of a circuit configuration of high-frequencypower amplifier 21 of the first embodiment. High-frequency poweramplifier 21 is the high-frequency power amplifier, which amplifies thehigh-frequency input signal and outputs the signal having one powerselected from a plurality of powers. High-frequency power amplifier 21includes input terminal 1 a to which the input signal is input and highoutput route 10 a that is the first output route. The first output routeis the circuit, which amplifies the input signal input to input terminal1 a and outputs the signal having the first power (in this case, a highoutput power). High-frequency power amplifier 21 also includes mediumoutput route 100 a that is the second output route. The second outputroute is the circuit, which amplifies the input signal input to inputterminal 1 a and outputs the signal having the second power (in thiscase, a medium output power). High-frequency power amplifier 21 alsoincludes output terminal 2 a that selectively outputs the signals outputfrom high output route 10 a and medium output route 100 a andbias/control circuit 3 a that controls high output route 10 a and mediumoutput route 100 a so as to selectively operate high output route 10 aand medium output route 100 a.

High output route 10 a includes switch element 15 a that is the fourthswitch element connected to input terminal 1 a, input matching circuit12 a that is connected to the output node of switch element 15 a, andhigh-output amplifier 11 a that is the first amplifier connected to theoutput node of input matching circuit 12 a. High output route 10 a alsoincludes output matching circuit 13 a that is the first output matchingcircuit connected to the output node of high-output amplifier 11 a andswitch element 14 a that is the first switch element connected to theoutput node of output matching circuit 13 a.

Medium output route 100 a includes switch element 115 that is the thirdswitch element connected to input terminal 1 a and input matchingcircuit 112 that is connected to the output node of switch element 115.Medium output route 100 a also includes medium-output amplifier 111 thatis the second amplifier connected to the output node of input matchingcircuit 112 and switch element 114 that is the second switch elementconnected between the output node of medium-output amplifier 111 and theoutput node of output matching circuit 13 a (in this case, switchelement 14 a).

Bias/control circuit 3 a is a circuit that controls high output route 10a and medium output route 100 a so as to selectively operate high outputroute 10 a and medium output route 100 a. Specifically, in the case thathigh output route 10 a is operated, bias/control circuit 3 a operateshigh-output amplifier 11 a by supplying a proper bias current tohigh-output amplifier 11 a, turns on switch elements 14 a and 15 a, andturns off other amplifiers and switch elements. On the other hand, inthe case that medium output route 100 a is operated, bias/controlcircuit 3 a operates medium-output amplifier 111 by supplying the properbias current to medium-output amplifier 111, turns on switch elements114 and 115, and turns off other amplifiers and switch elements.

High-frequency power amplifier 21 of the first embodiment having theabove configuration is operated as follows.

Next, the operation of high output route 10 a will be described. In highoutput route 10 a, the high-frequency power signal input from inputterminal 1 a is input to high-output amplifier 11 a through switchelement 15 a and input matching circuit 12 a. The high-frequency powersignal amplified by high-output amplifier 11 a is output from outputterminal 2 a through output matching circuit 13 a and switch element 14a.

During the operation of high output route 10 a, because of the controlperformed by bias/control circuit 3 a, switch elements 14 a and 15 a andhigh-output amplifier 11 a become an on-operation, and other switchelements and amplifiers are in an off-state. Bias/control circuit 3 a isconnected to a base terminal of high-output amplifier (HBT) 11 a, and acurrent is supplied to the base of high-output amplifier 11 a.

The operation of medium output route 100 a will be described below. Thehigh-frequency power signal input from input terminal 1 a is input tomedium-output amplifier 111 through switch element 115 and inputmatching circuit 112. The high-frequency power signal amplified bymedium-output amplifier 111 is output from output terminal 2 a throughswitch element 114.

During the operation of medium output route 100 a, bias/control circuit3 a is connected to a base terminal of medium-output amplifier (HBT)111, and the current is supplied to the base of medium-output amplifier111. At this point, a cell size of medium-output amplifier 111 isoptimized according to the output, and is smaller than that ofhigh-output amplifier 11 a. When the high-frequency power signal inputfrom input terminal 1 a is amplified by medium output route 100 a,switch elements 115 and 114 and medium-output amplifier 111 become theon-operation, and other switch elements and amplifiers are in theoff-state.

A size (specifically, a gate width of a transistor) of switch element 14a provided in high output route 10 a is larger than that of switchelement 114 provided in medium output route 100 a in order to pass thelarger power.

FIG. 2 illustrates a circuit of high-frequency power amplifier 21 of thefirst embodiment. Specifically, in this embodiment, a power output rangeof about 0 dBm to about 20 dBm is defined as “medium output”, and apower output range of about 21 dBm to about 30 dBm is defined as “highoutput”. Output terminal 2 a has an output impedance of 50Ω, and isconnected to a load (such as an antenna) of 50Ω.

In the first embodiment, high-output amplifier 11 a is the HBT in whichthe output impedance is set to 5Ω using the bias current by thebias/control circuit 3 a (setting of an operating point) during theoperation. Output matching circuit 13 a is an impedance converter, whichincludes an inductor and a capacitor, and has an input impedance of 5Ωand the output impedance of 50Ω. In the first embodiment, medium-outputamplifier 111 is the HBT in which the output impedance is set to 50Ωusing the bias current by the bias/control circuit 3 a (the setting ofthe operating point) during the operation. A relationship of P=V2/Zoutholds among output power P, amplitude voltage V of an output signal, andoutput impedance Zout in an amplifier, namely, an inversely proportionalrelationship holds between output power P and output impedance Zout whenamplitude voltage V of the output signal is kept constant. Accordingly,in the first embodiment, the output impedance of high-output amplifier11 a is set to 5Ω, and the output impedance of medium-output amplifier111 is set to 50Ω.

Thus in high-frequency power amplifier 21 of the first embodiment, anoutput matching circuit is not provided in the output node ofmedium-output amplifier 111, because the output impedance ofmedium-output amplifier 111 is set to 50Ω and matched with the outputimpedance (50Ω) of high-frequency power amplifier 21 (that is, theoutput matching circuit 13 a). Therefore, the circuit scale ofhigh-frequency power amplifier 21 is reduced because of the unnecessityof the output matching circuit in medium output route 100 a.

In the first embodiment, switch elements 14 a, 15 a, and 115 are an FET.In the first embodiment, switch element 114 is configured by an FET thatis connected at a plurality of stages (in this case, three stages).Specifically, in switch element 114, three circuits each of which isconfigured by a parallel connection of the FET and a resistor areconnected in series. In FIG. 2, voltage power-off (AC coupling)capacitor 4 a is connected between output terminal 2 a and a connectionpoint of switch element 14 a and switch element 114.

Collector power supply terminal 6 a supplies a voltage of 3.5 V to acollector of the HBT constituting high-output amplifier 11 a. In thecase that the high output power is obtained, switch element 114 becomesthe off-state because bias/control circuit 3 a applies a control signalof 0 V to a gate of each of the three FETs constituting switch element114. Bias/control circuit 3 a applies the control voltage of 3.5 V tothe gate of the FET constituting switch element 14 a, whereby switchelement 14 a performs the on-operation.

During the high output operation (that is, in the case that the power of28 dBm is output), the signal having voltage amplitude of about 8 V isoutput to the output node of switch element 14 a. Switch element 114 isconfigured by three depletion type FETs having a threshold of −0.7 V.That is, three parallel circuits each of which includes the FET and theresistor are connected in series as switch element 114 between voltagepower-off capacitor 4 a and medium-output amplifier 111. In switchelement 114 having the above configuration, the output voltage of 8 V ofthe high output route is divided into three, and the divided voltage isapplied between the source and drain of each FET constituting switchelement 114, so that isolation can sufficiently be ensured betweenvoltage power-off capacitor 4 a and medium-output amplifier 111.

On the other hand, in the case that the medium output power is obtained,switch element 114 performs the on-operation because bias/controlcircuit 3 a applies the control signal of 3.5 V to the gate of each ofthe three FETs constituting switch element 114. Bias/control circuit 3 aapplies the control voltage of 0 V to the gate of the FET constitutingswitch element 14 a, whereby switch element 14 a performs theoff-operation. During the medium output operation (that is, in the casethat the power of 18 dBm is output), the signal having the voltageamplitude of about 2.5 V is output to the output node of switch element114. Switch element 14 a is configured by the depletion type FETs havingthe threshold of −0.7 V. This is because the sufficient isolation can beensured between voltage power-off capacitor 4 a and high-outputamplifier 11 a when the one-stage FET is connected between voltagepower-off capacitor 4 a and high-output amplifier 11 a.

As described above, in high-frequency power amplifier 21 of the firstembodiment, the output matching circuit is not provided betweenmedium-output amplifier 111 and output terminal 2 a, because the outputimpedance of medium-output amplifier 111 constituting medium outputroute 100 a is matched with the output impedance (50Ω) required foroutput terminal 2 a. Therefore, the circuit scale of high-frequencypower amplifier 21 of the first embodiment is smaller than that of theconventional high-frequency power amplifier in which the output matchingcircuit is provided in medium output route 100 a. Additionally, inhigh-frequency power amplifier 21 of the first embodiment, it is notnecessary to provide the output matching circuit having frequencydependence in medium output route 100 a. Therefore, power efficiency isimproved during the band widening and medium output.

Second Exemplary Embodiment

FIG. 3 is a block diagram of high-frequency power amplifier 22 accordingto a second embodiment of the present invention. FIG. 4 is a viewillustrating an example of a circuit configuration of high-frequencypower amplifier 22 of the second embodiment. Although high-frequencypower amplifier 22 of the second embodiment basically includes the sameconfiguration as high-frequency power amplifier 21 of the firstembodiment, high-frequency power amplifier 22 differs fromhigh-frequency power amplifier 21 of the first embodiment in thathigh-frequency power amplifier 22 includes two high output routes 10 aand 10 b corresponding to two different frequency bands. A pointdifferent from that of the first embodiment will be described below.

High output route 10 b is a circuit that amplifies the signal having thefrequency band different from that of high output route 10 a. Highoutput route 10 b includes switch element 15 b that is the fourth switchelement connected to input terminal 1 a, input matching circuit 12 bthat is connected to the output node of switch element 15 b, andhigh-output amplifier 11 b that is the first amplifier connected to theoutput node of input matching circuit 12 b. High output route 10 b alsoincludes output matching circuit 13 b that is the first output matchingcircuit connected to the output node of high-output amplifier 11 b andswitch element 14 b that is the first switch element connected to theoutput node of output matching circuit 13 b.

Medium output route 100 a is a wide-band amplifier route for mediumoutput, and can amplify the signals having the two frequency bandscorresponding to two high output routes 10 a and 10 b.

Bias/control circuit 3 b is a circuit that controls high output routes10 a and 10 b and medium output route 100 a so as to selectively operatehigh output routes 10 a and 10 b and medium output route 100 a.Specifically, in the case that high output route 10 b is operated,bias/control circuit 3 b operates high-output amplifier 11 b bysupplying the proper bias current to high-output amplifier 11 b, turnson switch elements 14 b and 15 b, and turns off other amplifiers andswitch elements. The same as the first embodiment holds true for thecase that high output route 10 a is operated and the case that mediumoutput route 100 a is operated.

High-frequency power amplifier 22 of the second embodiment having theabove configuration is operated as follows. The operation of the highoutput route will now be described. In high output route 10 a, thehigh-frequency power signal input from input terminal 1 a is input tohigh-output amplifier 11 a through switch element 15 a and inputmatching circuit 12 a. The high-frequency power signal amplified byhigh-output amplifier 11 a is output from output terminal 2 a throughoutput matching circuit 13 a, switch element 14 a, and voltage power-offcapacitor 4 a.

During the operation of high output route 10 a, because of the controlperformed by bias/control circuit 3 b, switch elements 15 a and 14 a andhigh-output amplifier 11 a become the on-operation, and other switchelements and amplifiers are in the off-state. Bias/control circuit 3 bis connected to the base terminal of high-output amplifier (HBT) 11 a,and the current is supplied to the base of high-output amplifier 11 a.

On the other hand, under the control of bias/control circuit 3 b, highoutput route 10 b is operated in the case that the high-frequency signalhaving the frequency different from that of high output route 10 a isinput to input terminal 1 a. The high-frequency power signal is input tohigh-output amplifier 11 b through switch element 15 b and inputmatching circuit 12 b. The high-frequency power signal amplified byhigh-output amplifier 11 b is output from output terminal 2 a throughoutput matching circuit 13 b, switch element 14 b, and voltage power-offcapacitor 4 a in turn.

During the operation of high output route 10 b, because of the controlperformed by bias/control circuit 3 b, switch elements 15 b and 14 b andhigh-output amplifier 11 b become the on-operation, and other switchelements and amplifiers are in the off-state. Bias/control circuit 3 bis connected to the base terminal of high-output amplifier (HBT) 11 b,and the current is supplied to the base of high-output amplifier 11 b.

The operation of medium output route 100 a will be described below. Thehigh-frequency power signal input from input terminal 1 a is input tomedium-output amplifier 111 through switch element 115 and inputmatching circuit 112. The high-frequency power signal amplified bymedium-output amplifier 111 is output from output terminal 2 a throughswitch element 114 and voltage power-off capacitor 4 a.

During the operation of medium output route 100 a, bias/control circuit3 b is connected to the base terminal of medium-output amplifier (HBT)111, and the current is supplied to the base of medium-output amplifier111. At this point, the cell size of medium-output amplifier 111 isoptimized according to the output, and is smaller than that ofhigh-output amplifiers 11 a and 11 b. When the high-frequency powersignal input from input terminal 1 a is amplified by medium output route100, switch elements 115 and 114 and medium-output amplifier 111 becomethe on-operation, and other switch elements and amplifiers are in theoff-state. That is, when the medium output route 100 a is operated,switch elements 115 and 114 and medium-output amplifier 111 become theon-state and other switch elements and amplifiers are in the off-state,even if the high-frequency signal having the frequency corresponding tohigh output route 10 a is input to input terminal 1 a, and even if thehigh-frequency signal having the frequency corresponding to high outputroute 10 b is input to input terminal 1 a.

FIG. 4 illustrates a circuit of high-frequency power amplifier 22 of thesecond embodiment of the present invention. Specifically, in thisembodiment, the power output range of about 0 dBm to about 20 dBm isdefined as the “medium output”, and the power output range of about 21dBm to about 30 dBm is defined as the “high output”. Output terminal 2 ahas the output impedance of 50Ω, and is connected to the load (such asan antenna) of 50Ω.

In the second embodiment, high-output amplifier 11 b is the HBT in whichthe output impedance is set to 5Ω using the bias current by thebias/control circuit 3 b (the setting of the operating point) during theoperation. Output matching circuit 13 b is the impedance converter,which includes the inductor and the capacitor, and has the inputimpedance of 5Ω and the output impedance of 50Ω.

In the second embodiment, each of switch elements 15 a and 15 b isconfigured by one FET, and each of switch elements 14 a and 14 b isconfigured by FETs connected at a plurality of stages (in this case,three stages) like switch element 114.

Collector power supply terminals 6 a and 6 b supply the voltage of 3.5 Vto the collectors of the HBTs constituting high-output amplifiers 11 aand 11 b. In the case that the high output power is obtained, switchelement 114 becomes the off-state because bias/control circuit 3 bapplies the control signal of 0 V to the gate of each of the three FETsconstituting switch element 114. Bias/control circuit 3 b selectively(one of switch elements 14 a and 14 b) applies the control voltage of3.5 V to the gates of the three FETs constituting each of switchelements 14 a and 14 b according to the frequency of the input signal,whereby switch element 14 a or 14 b performs the on-operation.

During the high output operation (that is, in the case that the power of28 dBm is output) performed by high output route 10 a, the signal havingthe voltage amplitude of about 8 V is output to the output node ofswitch element 14 a. Switch element 114 is configured by the threedepletion type FETs having the threshold of −0.7 V. That is, threeparallel circuits each of which includes the FET and the resistor areconnected in series as switch element 114 between voltage power-offcapacitor 4 a and medium-output amplifier 111. In switch element 114having the above configuration, the output voltage of 8 V of the highoutput route is divided into three, and the divided voltage is appliedbetween the source and drain of each FET constituting switch element114, so that the isolation can sufficiently be ensured between voltagepower-off capacitor 4 a and medium-output amplifier 111. Thus, in thecase that high output route 10 a is operated, high output route 10 b isin the off-state like medium output route 100 a. Like switch element114, switch element 14 b has the configuration in which the threeparallel circuits, each of which includes the FET and the resistor, areconnected in series. Therefore, the isolation can sufficiently beensured between voltage power-off capacitor 4 a and high-outputamplifier 11 b.

Because the operation of high output route 10 b is identical to that ofhigh output route 10 a except that the frequency different from that ofhigh output route 10 a is input, the description of the operation ofhigh output route 10 b is omitted.

On the other hand, in the case that the medium output power is obtained,switch element 114 performs the on-operation because bias/controlcircuit 3 b applies the control signal of 3.5 V to the gate of each ofthe three FETs constituting switch element 114. Bias/control circuit 3 bapplies the control voltage of 0 V to the gate of each of the three FETsconstituting switch element 14 a and to the gate of each of the threeFETs constituting switch element 14 b, whereby switch elements 14 a and14 b perform the off-operation. During the medium output operation (thatis, in the case that the power of 18 dBm is output), the signal havingthe voltage amplitude of about 2.5 V is output to the output node ofswitch element 114. Each of switch elements 14 a and 14 b is configuredby the three depletion type FETs having the threshold of −0.7 V. Thus,the three-stage FET is connected between voltage power-off capacitor 4 aand high-output amplifier 11 a and the three-stage FET is also connectedbetween voltage power-off capacitor 4 a and high-output amplifier 11 b.Therefore, the isolation can efficiently be ensured between thesecomponents.

In high-frequency power amplifier 22 of the second embodiment, there isno limitation to the frequency of the signal amplified by medium outputroute 100 a because the matching circuit, which is configured by thecapacitance or inductor and connected to the collector of medium-outputamplifier (transistor) 111, is eliminated in medium output route 100 a.Therefore, medium output route 100 a can amplify not only the signalhaving the frequency corresponding to high output route 10 a but alsothe signal having the frequency corresponding to high output route 10 b,so that medium output route 100 a can be used in the wide band.

Third Exemplary Embodiment

FIG. 5 is a block diagram of high-frequency power amplifier 23 accordingto a third embodiment of the present invention. High-frequency poweramplifier 23 of the third embodiment basically includes the sameconfiguration as high-frequency power amplifier 21 of the firstembodiment and high-frequency power amplifier 22 of the secondembodiment. However, high-frequency power amplifier 23 differs fromhigh-frequency power amplifier 21 including one high output route in thefirst embodiment and high-frequency power amplifier 22 including twohigh output routes in the second embodiment in that high-frequency poweramplifier 23 includes M (≧3) high output routes 10 a, 10 b, . . . , and10 z corresponding to M different frequency bands. That is, theconfiguration of the third embodiment differs from those of the firstand second embodiments in the number of high output routes.

Accordingly, the high-frequency signals having the frequencies differentfrom one another are input to high-output amplifiers 11 a, 11 b, . . . ,and 11 z of the high output route.

Medium output route 100 a is the wide-band amplifier route for themedium output, and can amplify the signals having the M frequency bandscorresponding to M high output routes 10 a, 10 b, . . . , and 10 z.

Bias/control circuit 3 c is a circuit that controls high output routes10 a, 10 b, . . . , and 10 z and medium output route 100 a so as toselectively operate high output routes 10 a, 10 b, . . . , and 10 z andmedium output route 100 a. The third embodiment differs from the secondembodiment only in that the number of high output routes of controltargets increases.

The operation of high-frequency power amplifier 23 of the thirdembodiment having the above configuration is identical to that of thesecond embodiment except that the number of high output routesincreases. Therefore, the description of the operation of high-frequencypower amplifier 23 is omitted.

Fourth Exemplary Embodiment

FIG. 6 is a block diagram of high-frequency power amplifier 24 accordingto a fourth embodiment of the present invention. High-frequency poweramplifier 24 of the fourth embodiment basically includes the sameconfiguration as high-frequency power amplifier 23 of the thirdembodiment. However, high-frequency power amplifier 24 differs fromhigh-frequency power amplifier 23 including one output terminal 2 a inthe third embodiment in that high-frequency power amplifier 24 includesM output terminals 2 a, 2 b, . . . , and 2 z corresponding to highoutput routes 10 a, 10 b, . . . , and 10 z (that is, M differentfrequency bands). The configuration of the fourth embodiment differsfrom that of the third embodiment in the number of output terminals.

Like medium output route 100 a of the third embodiment, medium outputroute 100 b is the wide-band amplifier route for the medium output thatcan amplify the signals of the M frequency bands corresponding to M highoutput routes 10 a, 10 b, . . . , and 10 z. However, medium output route100 b differs from medium output route 100 a of the third embodiment inthat medium output route 100 b includes M switch elements 114 a, 114 b,. . . , and 114 z corresponding to M output terminals 2 a, 2 b, . . . ,and 2 z.

Bias/control circuit 3 d is a circuit that controls high output routes10 a, 10 b, . . . , and 10 z and medium output route 100 b so as toselectively operate high output routes 10 a, 10 b, . . . , and 10 z andmedium output route 100 b. In the case that medium output route 100 b isoperated, in addition to the control of the third embodiment,bias/control circuit 3 d performs control so as to turn on correspondingone of switch elements 114 a, 114 b, . . . , and 114 z according to theinput frequency (one of the M frequency bands).

The operation of high-frequency power amplifier 24 of the fourthembodiment having the above configuration is identical to that of thethird embodiment except that the control to turn on corresponding one ofswitch elements 114 a, 114 b, . . . , and 114 z is added in the casethat medium output route 100 b is selected. Therefore, the descriptionof the operation of high-frequency power amplifier 24 is omitted.

Fifth Exemplary Embodiment

FIG. 7 is a block diagram of high-frequency power amplifier 25 accordingto a fifth embodiment of the present invention. High-frequency poweramplifier 25 of the fifth embodiment basically includes the sameconfiguration as high-frequency power amplifier 24 of the fourthembodiment. However, high-frequency power amplifier 25 differs fromhigh-frequency power amplifier 24 including one input terminal 1 a inthe fourth embodiment in that high-frequency power amplifier 25 includesM input terminals 1 a, 1 b, . . . , and 1 z corresponding to high outputroutes 10 a, 10 b, . . . , and 10 z (that is, the M different frequencybands). The configuration of the fifth embodiment differs from that ofthe fourth embodiment in the number of input terminals.

Like medium output route 100 b of the fourth embodiment, medium outputroute 100 c is the wide-band amplifier route for the medium output thatcan amplify the signals of the M frequency bands corresponding to M highoutput routes 10 a, 10 b, . . . , and 10 z. However, medium output route100 c differs from medium output route 100 b of the fourth embodiment inthat medium output route 100 c includes M switch elements 115 a, 115 b,. . . , and 115 z corresponding to M input terminals 1 a, 1 b, . . . ,and 1 z.

Bias/control circuit 3 e is a circuit that controls high output routes10 a, 10 b, . . . , and 10 z and medium output route 100 c so as toselectively operate high output routes 10 a, 10 b, . . . , and 10 z andmedium output route 100 c. In the case that medium output route 100 c isoperated, in addition to the control of the fourth embodiment,bias/control circuit 3 e performs control so as to turn on correspondingone of switch elements 115 a, 115 b, . . . , and 115 z according to theinput frequency (one of the M frequency bands).

The operation of high-frequency power amplifier 25 of the fifthembodiment having the above configuration is identical to that of thefourth embodiment except that the control to turn on corresponding oneof switch elements 115 a, 115 b, . . . , and 115 z is added in the casethat medium output route 100 c is selected. Therefore, the descriptionof the operation of high-frequency power amplifier 25 is omitted.

Sixth Exemplary Embodiment

FIG. 8 is a block diagram of high-frequency power amplifier 26 accordingto a sixth embodiment of the present invention. High-frequency poweramplifier 26 of the sixth embodiment basically includes the sameconfiguration as high-frequency power amplifier 25 of the fifthembodiment. However, high-frequency power amplifier 26 differs fromhigh-frequency power amplifier 25 of the fifth embodiment in which highoutput routes 10 a, 10 b, . . . , and 10 z include no input switchelements in that high output routes 10 a, 10 b, . . . , and 10 z includeM input switch elements 15 a, 15 b, . . . , and 15 z, respectively. Inthe sixth embodiment, switch elements 15 a, 15 b, . . . , and 15 z areconnected between input terminals 1 a, 1 b, . . . , and 1 z and inputmatching circuits 12 a, 12 b, . . . , and 12 z of high output routes 10a, 10 b, . . . , and 10 z in order to improve the isolation between highoutput routes 10 a, 10 b, . . . , and 10 z and medium output routes 100c, respectively.

Bias/control circuit 3 f is a circuit that controls high output routes10 a, 10 b, . . . , and 10 z and medium output route 100 c so as toselectively operate high output routes 10 a, 10 b, . . . , and 10 z andmedium output route 100 c. In the case that high output routes 10 a, 10b, . . . , and 10 z are operated, in addition to the control of thefifth embodiment, bias/control circuit 3 f performs control so as toturn on corresponding one of switch elements 15 a, 15 b, . . . , and 15z according to the input frequency (one of the M frequency bands).

The operation of high-frequency power amplifier 26 of the sixthembodiment having the above configuration is identical to that of thefifth embodiment except that the control to turn on corresponding one ofswitch elements 15 a, 15 b, . . . , and 15 z is added in the case thathigh output routes 10 a, 10 b, . . . , and 10 z are selected. Therefore,the description of the operation of high-frequency power amplifier 26 isomitted.

Although the high-frequency power amplifiers according to the first tosixth embodiments of the present invention are described above, thepresent invention is not limited to the first to sixth embodiments.Various modifications, by a person skilled in the art, of eachembodiment and any combination of constituents of each embodiment arealso included in the present invention without departing from the scopeof the invention.

In the embodiments, the high-frequency power amplifier includes the highoutput route and the medium output route. Alternatively, thehigh-frequency power amplifier may include the low output route like theconventional high-frequency power amplifier. The low output route mayhave the same configuration as the conventional low output route or thesame configuration (the configuration that does not include the outputmatching circuit) as the medium output route of each of the embodiments.

In the embodiments, the high-output amplifier has the output impedanceof 5Ω, the output matching circuit in the high output route has theinput impedance of 5Ω, the output matching circuit in the high outputroute has the output impedance of 50Ω, and the medium-output amplifierhas the output impedance of 50Ω. However, the present invention is notlimited to the above impedance values. For example, the output matchingcircuit in the high output route and the medium-output amplifier mayhave the output impedance of 75Ω. As long as the output impedance of theoutput matching circuit in the high output route is matched with theoutput impedance of the medium-output amplifier, the necessity of theoutput matching circuit in the medium output route is eliminated toachieve the object of the present invention.

The present invention implements the band widening and high efficiencyof the high-frequency power amplifier, particularly in the medium outputroute, so that the present invention is useful as the high-frequencypower amplifier used in the mobile-communication transmitting deviceincluding the mobile phone.

What is claimed is:
 1. A high-frequency power amplifier that amplifies ahigh-frequency input signal and outputs a signal having one powerselected from a plurality of powers, the high-frequency power amplifiercomprising: a first output route that is a circuit, which amplifies theinput signal and outputs a signal of a first power; and a second outputroute that is a circuit, which amplifies the input signal and outputs asignal of a second power, wherein the first output route includes: afirst amplifier that amplifies the input signal; a first output matchingcircuit that is connected to an output node of the first amplifier; anda first switch element that is connected to an output node of the firstoutput matching circuit, and the second output route includes: a secondamplifier that amplifies the input signal; and a second switch elementthat is connected between an output node of the second amplifier and anoutput node of the first switch element, each of the first switchelement and the second switch element comprises a transistor, and a sizeof the first switch element is larger than a size of the second switchelement.
 2. The high-frequency power amplifier according to claim 1,wherein the first power is larger than the second power, each of thefirst amplifier and the second amplifier comprises a transistor, and acell size of the transistor constituting the first amplifier is largerthan a cell size of the transistor constituting the second amplifier. 3.The high-frequency power amplifier according to claim 1, wherein aninput impedance of the first output matching circuit is lower than aninput impedance of the second switch element.
 4. The high-frequencypower amplifier according to claim 1, wherein an output impedance of thefirst output matching circuit is equal to an output impedance of thesecond amplifier.
 5. The high-frequency power amplifier according toclaim 1, further comprising an output terminal that is connected betweenthe output node of the first switch element and an output node of thesecond switch element.
 6. The high-frequency power amplifier accordingto claim 1, further comprising: an output terminal that outputs anoutput signal from the high-frequency power amplifier; and a capacitorthat is connected between the output terminal and a connection point ofthe output node of the first switch element and the second switchelement.
 7. The high-frequency power amplifier according to claim 1,comprising a plurality of first output routes, each of which isidentical to the first output route, corresponding to differentfrequency bands.
 8. The high-frequency power amplifier according toclaim 1, wherein the first amplifier is connected to an output terminalthrough the first output matching circuit and the first switch element,and the second amplifier is connected to the output terminal through thesecond switch element.
 9. The high-frequency power amplifier accordingto claim 1, further comprising an input terminal to which the inputsignal is input, wherein the second output route further includes athird switch element that is connected between the input terminal and aninput node of the second amplifier.
 10. The high-frequency poweramplifier according to claim 9, wherein the first output route furtherincludes a fourth switch element that is connected between the inputterminal and an input node of the first amplifier.
 11. A high-frequencypower amplifier that amplifies a high-frequency input signal and outputsa signal having one power selected from a plurality of powers, thehigh-frequency power amplifier comprising: a first output route that isa circuit, which amplifies the input signal and outputs a signal of afirst power; and a second output route that is a circuit, whichamplifies the input signal and outputs a signal of a second power,wherein the first output route includes: a first amplifier thatamplifies the input signal; a first output matching circuit that isconnected to an output node of the first amplifier; and a first switchelement that is connected to an output node of the first output matchingcircuit, and the second output route includes: a second amplifier thatamplifies the input signal; and a second switch element that isconnected between an output node of the second amplifier and an outputnode of the first switch element, wherein the second switch elementcomprises transistors that are connected in a plurality of stages. 12.The high-frequency power amplifier according to claim 11, wherein thesecond switch element comprises a plurality of circuits being connectedin series, each of the plurality of circuits comprises a transistor anda resistor being connected in parallel.
 13. The high-frequency poweramplifier according to claim 11, further comprising an input terminal towhich the input signal is input, wherein the second output route furtherincludes a third switch element that is connected between the inputterminal and an input node of the second amplifier.
 14. Thehigh-frequency power amplifier according to claim 13, wherein the firstoutput route further includes a fourth switch element that is connectedbetween the input terminal and an input node of the first amplifier. 15.A high-frequency power amplifier that amplifies a high-frequency inputsignal and outputs a signal having one power selected from a pluralityof powers, the high-frequency power amplifier comprising: a first outputroute that is a circuit, which amplifies the input signal and outputs asignal of a first power; and a second output route that is a circuit,which amplifies the input signal and outputs a signal of a second power,wherein the first output route includes: a first amplifier thatamplifies the input signal; a first output matching circuit that isconnected to an output node of the first amplifier; and a first switchelement that is connected to an output node of the first output matchingcircuit, the second output route includes: a second amplifier thatamplifies the input signal; and a second switch element that isconnected between an output node of the second amplifier and an outputnode of the first switch element, and an input terminal to which theinput signal is input, wherein the second output route further includesa third switch element that is connected between the input terminal andan input node of the second amplifier.
 16. The high-frequency poweramplifier according to claim 15, wherein the first output route furtherincludes a fourth switch element that is connected between the inputterminal and an input node of the first amplifier.
 17. A high-frequencypower amplifier that amplifies a high-frequency input signal and outputsa signal having one power selected from a plurality of powers, thehigh-frequency power amplifier comprising: a first output route that isa circuit, which amplifies the input signal and outputs a signal of afirst power; and a second output route that is a circuit, whichamplifies the input signal and outputs a signal of a second power,wherein the first output route includes: a first amplifier thatamplifies the input signal; a first output matching circuit that isconnected to an output node of the first amplifier; and a first switchelement that is connected to an output node of the first output matchingcircuit, and the second output route includes: a second amplifier thatamplifies the input signal; and a second switch element that isconnected between an output node of the second amplifier and an outputnode of the first switch element, wherein an output impedance of thefirst amplifier is about 5Ω, an input impedance of the first outputmatching circuit in the first output route is about 5Ω, an outputimpedance of the first output matching circuit in the first output routeis about 50Ω, and an output impedance of the second amplifier is about50Ω.
 18. The high-frequency power amplifier according to claim 17,further comprising an input terminal to which the input signal is input,wherein the second output route further includes a third switch elementthat is connected between the input terminal and an input node of thesecond amplifier.
 19. The high-frequency power amplifier according toclaim 18, wherein the first output route further includes a fourthswitch element that is connected between the input terminal and an inputnode of the first amplifier.